Indonesian Multiscale Grid System for Environmental Data

Transcription

1 Indonesian Multiscale Grid System for Environmental Data Akhmad Riqqi, Anisa Fitria, Kosasih Prijatna, Radityo Egi Pratama, and John Mahmudy Abstract The diversity of environmental data will complicate the process of merging the data, it is among others caused by differences geodetic reference system, resolution, and the difference in pixel coordinates. Therefore, needed a system that can be used to standardize the national environmental data storage so that various types of environmental data can be stored and utilized. Grid system is a raster based data and very well used to store and represent information about geographic features continuous and gradual change. With the multi scale method, various types of national environmental data can be stored in a container that has been standardized and universally understandable. A multiscale grid system had successfully created to store various types of environmental data in a variety of scale, to the territory of Indonesia. Setting geodetic reference system, grid resolution, the point of origin grid coordinate system, and grid numbering system that will be used makes this system. 1. Introduction Environmental data is related data to environmental phenomena. Mostly environmental data is spatial data that covered entire or a part of earth surface. They were different in kind, for example temperature, carbon dioxide emission, vegetation, topography, etc. These data need for research, planning, and decisionmaking. The needed of environmental data is increasing because of some factor, namely, increasing of world population, necessity of sustainable development strategic, development of prediction methods for environmental phenomena, estimate potential and impact of disaster. Environmental data should be collected at local, county, province, national, regional and global level. Acquisition, validation, system for keeping archives, and sharing data system become the prime consideration to generate trustable information. In generating information often we should unite several data. Varieties of model and structure data oftentimes make that process complicated.

2 Data structure is method to store, configure, and arrange data in computer storage media in order that data can be used efficiently. Grid system is a kind of spatial data model and data structure used to store spatial data. In grid model data, a partial of area is representing using a grid with same size and used tessellation data structure. The difficulties of unification environmental data often caused by different geodetic reference system, resolution, and origin of coordinate system in grid or pixel based data. Normally to overcome this problem, data should be proceed with coordinate transformation and resampling data. These recur process generate the same problem in the future. This avoidable process can t be occurring if we have standardized system to store and visualize environmental data. This paper will describe a multiscale grid system for Indonesia area. The system can be used as a standardized systematic structure data to store data in a raster look like. 1.1 Objectives Since Indonesia has a wide area, it has own problem to determine grid system. The study has objective to create befit grid system in Indonesia for restore, investigate, and analysis environmental data. 1.2 Indonesian Mapping System Bakosurtanal s map is Indonesian Topography Map (RBI). The map is generated by Bakosurtanal comprises of scale 1: , 1: , 1: , 1:50.000, 1: and 1: where all Indonesia region divided into grids of systematically map size. All of the map s sheet are precise among one to another, and its size is same for each sheet. Size of sheet depends on the scale. Size of Indonesian Topography Map is related to the following UTM s grid system. The numbering system of Indonesian Topography Map is a numeric code. This number can recognize the location and map scale of area. The numbering systematic of map index in Indonesia is from 90 o EL and 15 o ST to North and East direction. Numbering system of Indonesian Topography map is from scale 1: (4 number) to scale 1: (8 number). This sheet numbering system has different digit of number for every scale, but there are relation-numbering system between sheets in different scale in the same location. 1.3 Methodology The following step were carry out to determined the grid system. Identify the posible grid system can be used in Indonesia area. Examine mapping system has been used for national spatial data. Determine the grid system.

3 Examine accuratness and give some example. 2. Multiscale Grid System 2.1 Grid System A grid is a regular tessellation of a manifold or 2-D surface that divides it into a series of contiguous cells, which can then be assigned unique identifiers and used for spatial indexing purposes. Grid system often used as data structures for global georeferenced data sets for multi-resolution partitions, such as discrete global grid. Discrete global grid (DGG) consists of a set of regions that form a partition of the Earth s surface, where each region has a single point contained in the region associated with it. A discrete global grid system (DGGS) is a series of discrete global grids Discrete global grid systems based on the geographic coordinate system have numerous practical advantages (Sahr et al, 2003). Varied grids have been proposed or are currently in use, including grids based on square cells, triangular grids or meshes, hexagonal grids, grids based on diamondshaped cells, and possibly more. Grids based on square partitions are by far the most familiar to users, and they map efficiently to common data structures and display devices. 2.2 Indonesian Multiscale Grid System Multiscale is a method used to describe a phenomena with monotonous pattern in scale with take advantage from information refer to range or a wide spectrum of scale simultaneously. This method is useful for record, investigate, describe and monitoring environmental phenomena. To perform this method, we need data as a source of information and structured them in hierarchic and systematic way. A discrete grid system is an approriate system to this need. For Indonesian area, its important to create the system compatible with current national mapping system, so we proposed Indonesian multiscale grid system (IMGS). IMGS has structure look like a raster data structure based on square cells, its suitable for store and visualize continuous geographic phenomena and change gradually. This grid model present, collocate, and store spatial data with matrix structure. Matrix is a rectangular array of quantities or expressions in rows and columns that is treated as a single entity and manipulated according to particular rules. This singel entity is a cell and in term of raster data model we call it pixel. Every cell has an atribute data

4 and unique coordinate. This system was developed by determine: geodetic reference system, resolution, origin, and cell numbering system. IMGS used DGN 95 datum as geodetic reference system. DGN (Datum Geodesi Nasional) 95 was define by Bakosurtanal in 1996 as national geodetic reference system for indonesian area (Matindas et.al., 1997). Geodetic coordinate system is used to present the location of grid with latitude and longitude. Resolution or size of cell in IMGS almost followed the size of sheet numbering system in RBI. But, IMGS using difference size of grid. In RBI numbering system, they have five size of grid for map sheet, from ( x 1 0 ) to (2 30 x 2 30 (5'' x 5''). The IMGS resolutions are 30', 15', 7' 30'',2' 30'', and 5''. Origin is an arbitary point which has been choosen as center of reference system. In the case of IMGS, origin point was chosen as left lower point of grid system. The origin point for IMGS is 90 o EL and 15 o ST. This is the same coordinate for numbering systematic of map index in Indonesia. To pointing the cell, not only using coordinate but the numbering system as an identity of cell (Id cell) was developed. The numbering system was modified from RBI sheet numbering system. Same as sheet numbering system for RBI, Id cell number depend on resolution of cell. Coarse cell have a few digit number than finer ones. The 5''x5'') cell size has 11 digit of numbers. See in figure 1 for cell numbering system. Fig 1. Example of IMGS cell numbering system. Description: K = grid 1 30' x 1 column number, for example, K = 12. B = grid 1 30' x 1 row number, for example, B = 09. C = grid 30' x 30' serial number on grid 1 30' x 1, for example C = 1. D = grid 15' x 15' serial number on 30' x 30', for example D = 2. E = grid 7' 30'' x 7' 30'' serial number on 15' x 15', for example E = 3. F = grid 2' 30'' x 2' 30''serial number on 7' 30'' x 7' 30'', for example F = 4. G = grid 5'' x 5'' serial number on 2' 30'' x 2' 30'', for example F = 100.

5 2.3 Accurateness The accuracy of this data model depends on resolution or cell size in earth surface. To know the accurateness of this grid system, the comparison of cell area and length of parallels and meridian in ellipsoid surface, map projection, and cell size in IMGS were conducted in every resolution to know distortion among them. Largest distortion in cell area and length of parallels and meridian were exist between cell grid IMGS and map projection, the distortion are 3,86%; 3,38% and 0,67% in (3 x 3 3,97%; 3,38% and 0,67% in (5 x 5 ) cell size. While distortions shape and size of cell in ellipsoid surface and map projection were smaller. These distortions are not influential to data quality. 3. Advantage and Example 3.1 Advantage The advantages of Indonesian multiscale grids system are: Standardize store system for national environmental data, so difference kind of data can be store in one place system. Integrating data for analysis or modeling can be done more easily. Environmental data that only cover small area still can be store and integrated with other data. Efficient way to store and sharing data in database. Data agregation and generalization between resolution or scale can be conduct easily. 3.2 Fauna Existence The need for existence of reliable spatial data is fundamental in the process of national development. The variety of fauna in Indonesia has made a new challenge in terms of fauna spatial data storage. Fauna spatial data are scattered in Indonesia. To collect them required storage system for all over fauna spatial data so that the various fauna data can be stored in one place and universally understood. Applicability of IMGS as a storage of spatial database can help the process of merging, storage, and displays various types of fauna existence data. This example was developt a spatial database using IMGS as a place for spatial database storage and provides the visualization of fauna existence information in webgis using Map Server. See in figure 2 for example of utilization of IMGS for sumateran elephant and

6 sumateran tiger existence in Aceh area using data from Fauna and Flora International (FFI) - Aceh. IMGS works well in storing, displaying, and updating data of fauna existence.

7 Figure 2. Visualizations of sumateran elepahant and tiger in Aceh area using 7'30'', 2'30'', and 5'' cell size. 3.3 Land Use and Land Cover Database

8 Figure 3. Visualizations of land use and landcover in Bandung area using 7'30'', 2'30'', and 5'' cell size. Information about land use and land cover is necessary for the government as the source of information for planning, monitoring, and decision making related to land use and land cover. In developing information of land use and land cover, IMGS has been used as a tools collect, store, and presents a collection of data. See figure 3, a spatial database of land use and land cover has been developed and designed using IMGS and presents in GIS Web by taking sample in Bandung area. The IMGS was not only useful for visualizing the data, but also useful and helpful in designing geodatabase. Identity cell (or Id cell) was used as primary key in table because it s a unique number and useful in aggregating data process to create a new dataset at coarse resolution. The visualization of different resolution of data was helpful to understand and to be informed. 4. Closing Indonesian multiscale grid system has been created by determine geodetic reference system, resolution, origin, and cell numbering system. IMGS is a helpful tools to collect, store, manage, analisys, and visualize spatial data. The system was develop based on national mapping system and therefore its compatible with national mapping system and can grow to be a national standar data structures for environmental data.

9 5. Reference Sahr et al, Discrete Global Grid Systems: Basic Definitions Discrete Global Grid. Cartography and Geographic Information Science, Vol. 30, No. 2, 2003, pp Bakosurtanal. Numbering System of Map Index. bakosurtanal/tutorial-2/. Acces: 14 September Matindas, R. W., C. Subarya dan R. Nataprawira Sistem Penomeran untuk PenunjukanPeta Rupabumi dalam Proyeksi UTM Datum Geodesi Nasional 1995 (DGN-1995). Pusat Pemetaan. BAKOSURTANAL.

10 Paper Reference No.: Title of the paper: Name of the Presenter: Author (s) Affiliation: PN69 Indonesian Multiscale Grid System for Environmental Data Akhmad Riqqi Akhmad Riqqi, Anisa Fitria, Kosasih Prijatna, Radityo Egi Pratama, and John Mahmudy Mailing Address: Labtek IX C Lantai 3 Teknik Geodesi dan Geomatika ITB Jl. Ganesha no 10 Bandung Address: akhmad.riqqi@gmail.com Telephone number (s): Fax number (s): Author(s) Photograph: